This invention relates to a structure for separating and prepositioning a set of fibers and a device designed to contain a set of separate fibers prepositioned using a structure according to the invention.
The invention is applicable to different domains including the connection of optical fibers to an optical device. The objective is then to put each optical fiber in line with a component, for example a microguide belonging to the optical device, as precisely as possible.
The problem that arises is the problem of alignment of the optical centerline of a fiber with the optical axis of the component. All types of manufacturing fluctuations (eccentricity of the core of fibers, variations on the outside diameter of fibers, dimensions of integrated optical devices, non-existence of precise mechanical marks) are all features that make the alignment difficult to achieve.
Some manufacturers of optical components deliver integrated components for which the connection to the fibers was already made in the factory. The component is then supplied with fiber pigtails that are fragile and consequently difficult to manipulate. The user must then take care not to damage them during all manipulation phases, and particularly during assembly of the component on an electronic card.
In the factory, the fibers are aligned with microguides either using mechanical precision marks, or by using xe2x80x9cactivexe2x80x9d alignment methods by coupling that consist of injecting light into one of the microguides and aligning the fiber by maximizing the coupled light content. These alignment methods are expensive and take time to be implemented, and require dedicated high precision equipment.
FIG. 1 shows a device for alignment by coupling of light. A ribbon 1 on which fibers 2 are fixed is placed facing an optical device 4. The optical centerline 6 of a microguide 5 is aligned with the optical centerline 3 of a fiber 2 using a light beam (not shown in the figure) to maximize optical transmission between the fiber and the microguide. Each optical fiber 2 is positioned in a notch formed in a support 7 that is then fixed to the optical device 4.
FIG. 2 shows a known alignment device using mechanical guidance. The device in FIG. 2 is commonly used for MT type rods. A ribbon 8 on which fibers are fixed is inserted by placing the fibers visually in the waves 9 with a circular or V-shaped bottom. The fibers are then slid into the cylindrical ducts 10, for example with a diameter of the order of 200 xcexcm for 125 xcexcm diameter fibers, over a distance D1, for example of the order of 1 mm. A conical connection 11 guides the fibers as far as the precision holes 12. Therefore with this method of alignment, an intermediate distance D1 is necessary so that the fiber can be inserted into the precision hole 12.
The initial preliminary guidance of the fibers is achieved by the waves 9. The fibers are not inserted into the cylindrical ducts directly, and they can be seen through an opening 13.
This device introduces the risk for the user that he will not be able to insert the fibers in the ducts in which they should be inserted. For example, this is the case of fiber 2b as shown in FIG. 2. A large angle can be achieved by adjustment of the ribbon 8 with width Dr within the recess 14 with width De. A fiber that stops firstly on the recess 14 (fiber 2a) can bend, thus enabling a fiber in this example located opposite the fiber 2a (FIG. 2b) to enter a duct that is not intended for it (duct 10a, whereas the duct that should contain the fiber 2b is duct 10b). This positioning error may make the fiber strip unusable. The only way to avoid this malfunction is extremely good eyesight and tactile skill.
Other solutions are known according to prior art. Thus, the patterns by which fibers can be aligned may be in the form of notches engraved directly in the optical component. An optical fiber built into a notch is then put directly facing a microguide. This type of connection has the advantage that it is not necessary to implement the alignment by coupling of light. However, the size of the notches was not adjusted to the size of the fibers, consequently the alignment of optical axes between the fibers and microguides remains difficult.
U.S. Pat. No. 5,440,657 discloses a splice in which the ribbon is guided by a casing with a structure in which the angle of approach enables fibers to be guided towards the alignment ducts separated by edges. The use of this type of alignment method causes high scrap rates since the natural dispersion of stripped fibers at the output from the ribbon is such that the fibers can slide on the edges that separate the ducts and consequently be directed toward the wrong duct. The only way to get around the problem is if the operator is highly skilled and takes special care. Therefore, this type of alignment device is not suitable for mass production or for wiring that has to be done by the final customer.
The invention does not have these disadvantages.
The invention relates to a structure for separating and prepositioning a set of fibers in which the fibers are inserted so that they can be separated and prepositioned. The structure comprises at least one recess that will contain and preposition a single fiber, the recess comprising a bottom wall, a top wall and at least one side wall formed by the side wall of a first pattern, the pattern having a front edge that is oblique with respect to the bottom wall of the recess and that goes from the bottom wall of the recess as far as a top part of the pattern, the side wall having at least one inclined connecting surface connecting the front oblique edge to the rest of the side wall, the top part of the pattern being at a distance from the top wall at the highest point of the front edge equal to a distance H less than or equal to one fiber diameter.
The recess of each fiber is defined on the sides by two walls. A first wall is formed by a side wall of a first pattern, the other side wall being formed by a side wall of a second pattern adjacent to the first pattern, or by a side wall of the body of the structure.
The walls have been called xe2x80x9ctop wallxe2x80x9d and xe2x80x9cbottom wallxe2x80x9d simply for clarity of the description, but obviously the structure can be in any position in space; thus, the concepts of xe2x80x9ctopxe2x80x9d, xe2x80x9cbottomxe2x80x9d, and even xe2x80x9csidexe2x80x9d are all relative to an arbitrary reference plan.
Advantageously, the distance H is less than the diameter of the fiber to avoid any risk of bad assembly.
The invention also relates to a device adapted to contain a set of separate fibers prepositioned using a structure according to the invention. The device and the structure form a particularly precise fiber positioning system. For each fiber, the device comprises a guidance zone and a reception notch formed by a narrowing of the guidance area.
In the application for the connection of optical fibers to an optical device, the separation and prepositioning structure according to the invention advantageously enables fixing each optical fiber in a position such that the fibers can easily by aligned with the optical device, regardless of the initial position of the fibers.